Citation
Bemmel, T. van. (2010, February 4). High blood pressure at old age : The Leiden 85 plus study. Retrieved from https://hdl.handle.net/1887/14652
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High blood pressure at old age
The Leiden 85 plus study
Thomas van Bemmel
Cover illustration: The vascular system, anatomical figure. Approx. 1490.
Leonardo Da Vinci
Layout and printed by: Gildeprint Drukkerijen - Enschede, The Netherlands
High blood pressure at old age
The Leiden 85 plus study
Proefschrift
ter verkrijging van
de graad van doctor aan de Universiteit van Leiden, op gezag van Rector Magnificus prof.mr. P.F. van der Heijden,
volgens besluit van het College voor Promoties te verdedigen op dinsdag 4 februari 2010
klokke 15.00
door
Thomas van Bemmel geboren te Arnhem
in 1969
Prof. dr. J. Gussekloo
Promotiecommissie:
Prof. dr. J.J. Bax Dr. G.J. Blauw Prof. dr. R.O.B Gans Prof dr. A.J. Rabelink
Aan Annemarie, Lucas en Marit
Contents
Chapter 1 Introduction 9
Chapter 2 In a population-based prospective study, 23 no association between high blood pressure and
mortality after age 85 years.
Chapter 3 Prospective study of the effect of blood pressure 39 on renal function in old age; The Leiden 85-plus Study.
Chapter 4 The effect of age on the association of blood 57 pressure with cognitive function later in life.
Chapter 5 Low blood pressure in the very old, a consequence 75 of imminent heart failure: the Leiden 85-plus Study.
Chapter 6 Prevalence of valvular heart disease in nonagenarians 91 from the general population: the Leiden 85-plus study.
Chapter 7 Markers of autonomic tone on a standard ECG are 107 predictive of mortality in old age.
Chapter 8 Discussion 123
Chapter 9 Summary 133
Chapter 10 Samenvatting 141
List of publications 149
Curriculum Vitae 151
C hapter 1
Introduction
Introduction
11 The last decades have shown an increasing interest in treatment of high blood
1
pressure. Copious amounts of data have been published on the mortality and morbidity risks of high blood pressure. [1] Overall these data have resulted in an increasing awareness of the deleterious effects of only modest elevation of blood pressure on morbidity and mortality. Moreover, treatment of high blood pressure resulted in substantial benefits in terms of reduced morbidity and mortality. [2- 6] This has resulted in official guidelines about treatment for hypertension that have become stricter with every decade. However, most of the evidence has been generated from middle-aged people. Only a few trials have included people of 80 year and older. [7-9] Looking at the results in detail within that age group the evidence is not robust. Given the increasing lifespan worldwide, physicians are confronted with many elderly patients over eighty. Hence, there is an increasing urge to generate more knowledge in regard to the effects of high blood pressure in the elderly.
Even in ancient times, high blood pressure has been recognized as a potential health threat. In the Yellow Emperor’s Classics of Internal Medicine, the following answers were given to the plain questions of the emperor of China, 2600 B.C [10]:
“The blood current flows continuously in a circle and never stops.”
“When the heart pulse beats vigorously and the strokes markedly prolonged, the corresponding illness makes the patient unable to speak.”
“If too much salt is used in food, the pulse hardens.”
More than 4000 years elapsed before William Harvey in 1628 proved the circulation of the blood; still later the sequence of hypertension, cerebral haemorrhage, and aphasia was recognized. [11] A hundred years later, Stephen Hales managed to measure systolic arterial blood pressure and the effect of haemorrhage on arterial blood pressure. [12] He also determined that the capillary arteries were the site of the chief peripheral resistance. The latter observation remains a basic concept in modern human physiology. In the early nineteenth century it became possible to measure blood pressure with a mercury manometer; it was used until 1896 when Scipione Riva-Rocci of Turin designed the first clinically acceptable sphygmomanometer. [13] In 1905 Korotkoff reported the now standard clinical procedure on the auscultatory method of determining systolic and diastolic blood pressure. [14]
At the beginning of the twentieth century there were three schools of thought with reference to the pathogenesis of hypertension. [15] First, the school of Bright that believed that essential hypertension was due to renal disease. [16] In 1827 Bright associated hardness and fullness of the pulse with albuminuria, edema and hypertrophy of the left ventricle with contracted kidneys. Thus, Bright introduced the concept of renal disease at the base of cardiovascular disease. Second, the school of Gull and Sutton believed that primary generalized arteriocapillary fibrosis caused contracted kidneys and left ventricular hypertrophy causing hypertension.
[17] Hence regarding hypertension as the result of widespread vascular disease.
Third, the school of Huchard and Allbutt making the statement that hypertension could occur without renal disease. [18,19] Years before, Mahomed had already published his clinical observation showing that high arterial blood pressure could exist without albuminuria. [20] Due to his untimely death, it wasn’t until Huchard and Allbutt’s finding that it was more widely established that arteriosclerosis and hypertension were independently associated diseases. These concepts were evaluated further in the early thirties of the 20th century mainly after Goldblatt could make dogs hypertensive after constricting their renal arteries. [21] In 1940, this resulted in the discovery of renin and finally in the discovery of the renin- angiotensin system. Nowadays many forms of secondary hypertension have been acknowledged, but the most frequent diagnosis remains essential hypertension.
Though the pharmacological treatment has expanded explosively, still no definite pathophysiological process has been recognized as the sole determinant of essential hypertension.
Although high blood pressure was known to have deleterious effects on health, the ultimate prognosis was considered to be different according to the underlying cause of hypertension. For example, in 1953 the arteriosclerotic form of hypertension in the elderly associated with arteriosclerosis of the large vessels, e.g. resulting in a wide pulse pressure, was supposed to have a benign prognosis. [22] Presently this is recognized as a common, but by no means, benign form of hypertension and referred to as isolated systolic hypertension. [23] Up to the late seventies of the 20th century only diastolic blood pressure was considered to be detrimental and was used to classify subjects who suffer from hypertension. [24] Later on, systolic blood pressure became recognized as an even stronger predictor of morbidity and mortality than diastolic blood pressure. Presently, goal levels of systolic blood
Introduction
13 pressure should be attained lower than 140 mmHg and for individuals with renal
1
disease and diabetes even lower than 130 mmHg, irrespective of age. [23]
According to the recent guidelines, hypertension has a very high prevalence amongst elderly. [23] In the Framingham study one could discern the average diastolic and systolic blood pressure increased up to the sixth decade resulting in a prevalence of hypertension up to 40% at the age of sixty. [25,26] From that point on the systolic blood pressure continued to rise up to the eighth decade, however the diastolic blood pressure started to decline.
Figure 1. Average age trends in (a) systolic and (b) diastolic blood pressure levels for men and women based on cross-sectional (dotted lines) and longitudinal (cohort, unbroken lines) data on participants in the Framingham Study. [26]
In another report the prevalence of hypertension reached 60% in persons aged 85 and over. [27] Given this high prevalence, many are reluctant in accepting the strict criteria for high blood pressure at middle age for people at old age, as most of the population eventually will fulfil these criteria.
It is argued that a high blood pressure at old age might have a different effect on health compared to same levels of blood pressure in the middle aged. This has been proven for other cardiovascular risk factors also. For example in persons aged 85 years and older total cholesterol levels were no longer related to mortality. [28]
Additionally observational data have shown that high blood pressure in elderly persons; above 80 years is no longer a risk factor for mortality. [27, 29, 30] Placebo- controlled clinical trials are not conclusive. Few subjects older than 80 years are included in these studies [2-6, 8]. An open-randomised trial has been published with patients exclusively over eighty years old. [7] In the treated group there was a non-significant increase in mortality that completely nullified the significant reduction in strokes. In contrast, the HYVET study, a placebo controlled double blind trial in persons aged 80 years and older, was prematurely stopped after safety analysis showed excess mortality in the placebo group. [9]
The differences in outcome between the observational and interventional studies at old age versus younger age are difficult to understand. In younger subjects the observational studies are in line with the intervention studies. A high blood pressure is related with greater mortality/morbidity and lowering high blood pressure reduces the mortality/morbidity. It is counterintuitive that high blood pressure at old age suddenly appeared not to be a risk factor; even more, that treatment of high blood pressure at old age may prove harmful. Possibly the elderly, as a group, are not so heterogeneous compared to the middle aged people. Treatment of high blood pressure in more diseased elderly might have more harmful effects compared to treatment in less diseased elderly. In younger age groups who are more vascular diseased, it has been reported that treatment for high blood pressure resulting in low diastolic blood pressure might give excess morbidity and mortality as well. [31, 32] In this thesis we have explored the predictive value of blood pressure and the possible underlying mechanism for the above-mentioned contradictory findings. This thesis consists of a general
Introduction
15 introduction, a prognosis part, an etiological insight part, a general discussion and
1
a summary.
Prognosis:
Is high blood pressure at older age associated with adverse outcomes, including cardiovascular mortality, renal failure and cognitive decline?
Etiological insights:
What is the association between blood pressure and cardiac function at older age?
We have used data of the Leiden 85-plus Study and the Rotterdam Study. The Leiden 85-plus Study was a prospective population-based study of all 85 years old inhabitants of Leiden, The Netherlands.[33] Between September 1997 and September 1999 all 705 members of the 1912 to 1914-birth cohort in the city of Leiden were asked to participate in this study in the month after their 85th birthday.
There were no selection criteria related to health or demographic characteristics.
At baseline, 85 year old participants were visited at their place of residence.
During these visits blood pressure was measured twice, an electrocardiogram recorded, a face-to-face interview taken and performance tests were conducted.
The participants were annually visited up to age 90 years old. At this age, a sample was invited to the study-centre for an echocardiographic examination.
The collected data provided unique opportunities to examine population wise the effects of blood pressure at old age.
The Rotterdam Study is a large, prospective, population-based cohort study conducted in all inhabitants aged 55 and older of Ommoord, a district of Rotterdam, The Netherlands. [34] Of 10,275 eligible subjects, 7,983 (77.7%) participated in the baseline examinations between 1990 and 1993 (mean age 71.2±25.2, range 55–106).
All participants were interviewed at home and visited the research centre for further examinations. At the fourth survey (2002–2004), cognitive function was extensively assessed using a dedicated neuropsychological test battery.
In the first part three studies on prognosis of blood pressure are presented.
Chapter two presents the association between blood pressure at age 85 years and mortality in the following 5 years. Chapter three presents the association between
blood pressure and creatinine clearance at the age of 85 years up to the age of 90 years. Chapter four describes the association between blood pressure and cognitive function over time. In the second part, three etiological oriented studies are presented. Chapter five describes the prevalence of cardiac valve dysfunction in participants aged 90 years. Chapter six describes the association between blood pressure and cardiac function at the age of 90 years. Chapter seven studies the possible connection between the autonomous nervous system and mortality in subjects 85 years and older. The eighth chapter contains a general discussion of the preceding studies chapters and their possible implications for care of older people with high blood pressure. The ninth chapter reveals the summary in English and Dutch.
Introduction
17
References 1
1. Prospectives Studies Collaboration. Age-specific relevance of usual blood pressure to vascular mortality: a meta-analysis of individual data for one million adults in 61 prospective studies. Lancet 2002;360:1903-13
2. SHEP Cooperative Research Group. Prevention of stroke by antihypertensive drug treatment in older persons with isolated systolic hypertension. JAMA 1991;265:3255-64
3. Dahlöf B, Lindholm LH, Hansson L, Scherstén B, Ekbom T, Wester P-O. Morbidity and mortality in the swedish trial in old patients with hypertension. Lancet 1991;338:1281-5
4. Staessen JA, Fagard R, Thijs L, et al. Randomised double-blind comparison of placebo and active treatment for older patients with isolated systolic hypertension.
Lancet 1997;350:757-64
5. Liu L, Wang JG, Gong L, Liu G, Steassen JA. Comparison of active treatment and placebo in older chinese patients with isolated systolic hypertension. J Hypertens 1998;16:1823-9
6. Staessen JA, Gasowski J, Wang JG, et al. Risks of untreated and treated isolated systolic hypertension in the elderly: meta-analysis of outcome trials. Lancet 2000;355:865-72
7. Bulpitt CJ, Beckett NS, Cooke J, et al. Results of the pilot study for the hypertension in the very elderly trial. J Hypertens 2003;21:2409-17
8. Gueyffier F, Bulpitt C, Boissel JP, et. al. Antihypertensive drugs in very old people:
a subgroup meta-analysis of randomised controlled trials. Lancet 1999;353:793-6 9. Beckett NS, Peters R, Fletcher AE, et al. Treatment of hypertension in patients 80
years of age or older. N Engl J Med; 2008; 358:1887-98.
10. The Yellow Emperor’s Classics of Internal Medicine. Translated by Ilza Veith.
Wiliams & Wilkins, 1949
11. Robert Willis M.D. The works of William Harvey M.D. Anatomical Essay on the Motion of the Heart and Blood in Animals. (Translated from Latin to English) London Sydenham Society. 1847
12. Hales S: Statical Essays: Containing Haemastaticks; or, an Account of Some Hydraulick and Hydrostatical Experiments Made on the Blood and Blood-Vessels of Animals. Ed. 1, London, W. Innys, R. Manby, and T. Woodward, 1733, vol. II.
13. Riva-Rocci S. Un Nuovo sfigmomanometro. Gazz Med Torino 1896;47:981 14. Korotkoff NS. On methods of studying blood pressure. Izv VoennomedAkad
1905;11:365
15. Wakerlin GE. From bright toward light: The story of hypertension research.
Circulation 1962;26:1-6
16. Bright R. Reports of medical cases. Selected with a view of illustrating the symptoms and cure of diseases by a reference to morbid anatomy. London, Longman, Rees, Orme. Brown and Green. 1827
17. Gull WW, Sutton HG. On the pathology of the morbid state commonly called chronic Bright’s disease with contracted kidney (‘Arterio-capillary fibrosis’). Med Chir Trans 1872; 55:273-326
18. Huchard H. Maladies du Coeur et des vaisseaux. Paris, Doin 1889
19. Allbutt TC. Senile plethora or high arterial pressure in elderly persons. Trans Hunterian Soc 1896; 96:38-57
20. Mahomed FA: The etiology of Bright’s disease and the pre-albuminuric stage.
Med Chir Trans 1874; 57:197-228
21. Goldblatt H, Lunch J, Hanzal RF, Summerville WW. The production of persistent elevation of systolic blood pressure by means of renal ischemia. J Experim Med 1934; 59:347-381
22. Hoobler SW. Treatment of hypertension in the elderly patient. J Am. Geriatrics.
Society 1954;2:108-113
23. The task force for the management of arterial hypertension of the European society of hypertension and of the European society of cardiology. 2007 Guidelines for the management of arterial hypertension. J Hypertension 2007;25:1105-1187
24. Report of the Joint National Committee on detection, evaluation and treatment of high blood pressure: a cooperative study. JAMA 1977;237:255-261
25. Franklin SS, Gustin IV W, Wong ND, Larson MG, Weber MA, Kannel WB, et al. Hemodynamic patterns of age-related changes in blood pressure. The Framingham heart study. Circulation 1997;96:308-15
26. Vokonas PS, Kannel WB, Cupples LA. Epidemiology and risk of hypertension in the elderly: the Framingham study. J Hypertens 1988;6(suppl 1):S3-S9
27. Boshuizen HC, Izaks GJ, Van Buuren S, Ligthart GJ. Blood pressure and mortality in elderly people aged 85 and older. BMJ 1998;316:1780-4
28. Weverling-Rijnsburger AW, Jonkers IJ, van Exel E, Gussekloo J, Westendorp RG.
High-density versus low-density lipoprotein cholesterol as the risk factor for coronary artery disease and stroke in old age. Arch Intern Med 2003;163:1549-54 29. S Rastas, Pirtillä T, Viramo P, Verkkoniemi A, Halonen P, Juva K, et al. Association
between blood pressure and survival over 9 years in a general population aged 85 and older. J Am Geriatr Soc 2006;54:912-18
Introduction
19
1
30. Heikinheimo RJ, Haavisto MV, Kaarela RH, Kanto AJ, Koivunen MJ, Rajala SA.
Blood pressure in the very old. J Hypertens 1990;8:361-7
31. Fagard RH, Staessen JA, Thijs L, Celis H, Bulpitt CJ, de Leeuw PW, Leonetti G, Tuomilehto J, Yodfat Y. On-treatment diastolic blood pressure and prognosis in systolic hypertension. Arch Int Med 2007;167:1884-91
32. Messerli FH, Mancia G, Conti CR, Hewkins AC, Kupfer S, Champion A, kolloch R, Benetos A, Pepine CJ. Dogma deputed: Can aggressively lowering blood pressure in hypertensive patients with coronary artery disease be dangerous? Ann Intern Med 2006;144:884-893
33. Bootsma-van der Wiel A, van Exel E, de Craen AJ, et al. A high response is not essential to prevent selection bias. Results from the Leiden 85-Plus Study. J Clin Epidemiol 2002;55:1119-25
34. Hofman A, Breteler MMB, van Duijn CM, et al. The Rotterdam Study: objectives and design update. Eur J Epidemiol 2007;22:819-829.
F irst p art
Prognosis
C hapter 2
In a population-based prospective study no association between high blood pressure and mortality after age 85 years.
Thomas van Bemmel, MD, Jacobijn Gussekloo, MD PhD, Rudi GJ Westendorp, MD PhD, Gerard J Blauw, MD PhD
Department of Gerontology and Geriatrics, Leiden University Medical Center, Leiden, the Netherlands.
J Hypertension 24:287-292, 2006
Abstract
Objective: To study the impact of a history of hypertension and current blood pressure on mortality in the oldest old.
Design: An observational population-based cohort study.
Setting: Community city of Leiden, the Netherlands.
Participants: Five hundred and ninety-nine inhabitants of the birth-cohort 1912- 1914 were enrolled on their 85th birthday. There were no selection criteria related to health or demographic characteristics.
Interventions: The mean follow-up was 4.2 years. The medical histories were obtained from general practitioners. Medication histories were obtained from the participant’s pharmacist. Blood pressure was measured twice at baseline.
Main outcome measures: All cause and cardiovascular mortality.
Results: Five hundred and seventy-one participants were included, 39.2%
had a history of hypertension. During follow-up 290 participants died, 119 due to cardiovascular causes. Compared to participants without a history of hypertension, those with a history of hypertension had increased mortality from cardiovascular causes [relative risk (RR) 1.60, confidence interval (CI) 1.06-2.40]
but equal mortality from all causes (RR 1.19, CI 0.91-1.55). High blood pressure at baseline (age 85) was not a risk factor for mortality. Baseline blood pressure values below 140/70 mmHg (n=48) were associated with excess mortality, predominantly in participants with a history of hypertension.
Conclusion: In the oldest old, high blood pressure is not a risk factor for mortality, irrespective of a history of hypertension. Blood pressure values below 140/70 are associated with excess mortality.
No association between high blood pressure and mortality.
25
2
Introduction
The role of high blood pressure as a risk factor for morbidity and mortality in the oldest old is still subject to debate, despite the fact that people aged 85 years and older often have a history of hypertension [1-9]. The relatively scarce observational data in people aged 80 years and over are contradictory, showing either an increased risk or an inverse relationship for high blood pressure with mortality [4-8].
Some of the different results found might be due to the differences between current blood pressure and former blood pressure [5]. Normal blood pressure in the face of a longstanding history of hypertension might have a considerable different impact on prognosis than high blood pressure without a history of hypertension.
Placebo-controlled clinical trials are also inconclusive, because hardly any subjects older than 80 years are included in these studies [2,10-14]. The only study designed for people older than 80 years reported a reduced risk for strokes but an increased total mortality rate in the actively treated group [2]. Those findings could be arguments for clinicians to be reluctant to treat high blood pressure in old age.
The aim of the present study was to disentangle the relationship between a positive history of hypertension and current blood pressure in very old men and women participating in the population-based Leiden 85-plus Study. With this study we elaborate on the previous findings in the former cohort of the Leiden 85-plus Study, showing that elevated blood pressure was associated with better survival in this age group [4].
Methods
Study population
The Leiden 85-plus Study is a prospective population-based study of all 85-year old inhabitants of Leiden, The Netherlands. The study design and characteristics of the cohort have been described in detail previously [15,16]. In short, between September 1997 and September 1999 all 705 members of the 1912 to 1914-birth cohort in the city of Leiden were asked to participate in the month after their 85th birthday. There were no selection criteria related to health or demographic characteristics.
At baseline, 85-year old participants were visited three times at their place of residence to administer extensive data on health, functioning and well-being. In addition, a medical history was obtained from participant’s general practitioner or nursing home physician, and information on the use of medication was obtained from participant’s pharmacist. Participants gave oral informed consent and for people who were severely cognitively impaired, a guardian gave informed consent. The Medical Ethics Committee of the Leiden University Medical Center approved the study.
History of hypertension and baseline blood pressure
The definition of a positive history of hypertension was fulfilled when at baseline the diagnosis hypertension could be obtained from the medical records. This was assessed independently of the baseline blood pressure (age 85 years).
An experienced research nurse measured blood pressure twice at baseline with a mean interval of 2 weeks. Blood pressure was measured in seated position after at least 5 min of rest and no vigorous exercise during the preceding 30 min. The cuff was inflated to 30 mmHg above the pressure after the disappearance of the radial pulse. The systolic value was measured at the onset of Korotkoff phase 1 and the diastolic value was measured at the onset of Korotkoff phase 5. For the analysis of blood pressure we used the mean of the measured systolic values and the mean of the measured diastolic blood pressures.
No association between high blood pressure and mortality.
27
2
Mortality
All participants were followed for mortality up until the censor date (1 April 2004). Shortly after the civil registry reported the death of a participant, the general practitioner or nursing home physician was interviewed to obtain the specific cause of death. Two senior specialists of internal medicine determined the primary causes of death by consensus without knowledge of medical history and the research aims. Primary causes of death were classified according to the tenth version of the International Classification of Diseases (ICD-10) [17] and were divided into two groups: cardiovascular mortality (ICD-codes I00-I99, I20-I25 and I60-I69) and non-cardiovascular mortality (all other ICD-codes).
Demographic and clinical characteristics
At baseline, a research nurse collected information concerning the demographic characteristics. Low education was defined as primary school only. At baseline the Mini-Mental State Examination (MMSE) was administered to screen for cognitive impairment [18]. Disability in basic activities of daily living (ADL) and instrumental activities of daily living (IADL) were assessed with the Groningen Activity Restriction Scale [19]. The presence of cardiovascular disease was defined as a previous history of cerebrovascular accident, angina pectoris, myocardial infarction, peripheral vascular disease or an electrocardiogram revealing myocardial ischaemia or infarction (Minnesota codes 1-1, 1-2, 1-3, 4-1, 4-2, 4-3, 5-1, 5-2 and 5-3) [20]. The presence of chronic disease was defined as a previous history of diabetes, Parkinson’s disease, chronic obstructive pulmonary disease, arthrosis, or malignancies. Angiotensin converting enzyme inhibitors, angiotensin-1 receptor blockers, thiazide diuretics, dihydropyridin calcium channel blockers or β-blockers with the exclusion of sotacor, were classified as antihypertensive drugs.
Baseline blood pressure categories
According to national and international guidelines, we categorized the participants for both systolic and diastolic blood pressure in three clinically relevant groups, namely a systolic blood pressure lower than 140 mmHg (normal blood pressure), 140-159 mmHg (hypertension stage 1) and 160 mmHg and over (hypertension stage 2) [21]. For diastolic blood pressure we used lower than 70 mmHg (low blood pressure), 70-89 mmHg (normal blood pressure) and 90 mmHg and over (hypertension stage 1 and 2) [7,21].
Statistical analysis
Distributions of categorical clinical characteristics were compared with chi- squared tests, and continuous data were compared with independent t-tests.
Mortality risks and 95% confidence intervals for participants with hypertension versus those without a history of hypertension were estimated in a Cox proportional-hazards model. We adjusted the mortality risks for gender, number of used antihypertensive medications and the presence of cardiovascular disease, because these determinants were differently distributed in the participants with and without a history of hypertension. The association between all-cause mortality and systolic and diastolic blood pressure was first visualized by use of Kaplan- Meier analyses, and differences were tested by log-rank tests. Mortality risks and 95% confidence intervals depending on systolic and diastolic blood pressure were estimated in a Cox proportional-hazards model. We adjusted the mortality risks for gender, use of antihypertensive medication and the presence of cardiovascular disease. To estimate the absolute risks of mortality, mortality rates and corresponding 95% confidence intervals were calculated by life tables for strata of systolic and diastolic blood pressure. All analyses were performed with SPSS version 12.01 (SPSS Inc., Chicago, Illinois, USA).
Results
Of the 705 eligible participants, 14 died before they could be enrolled and 92 refused to participate, resulting in a cohort of 599 participants (87% response).
In the present analyses we included only the 571 participants for whom two measurements of blood pressure at baseline were available.
At baseline, 224 participants (39.2%) had a history of hypertension according to the medical records of their general practitioner or nursing home doctor. The history of hypertension was equally distributed for gender and education (Table 1). There were no differences in daily functioning (both ADL and IADL), cognitive function and the presence of chronic diseases for those with and without a history of hypertension (Table 1). Participants with a history of hypertension more often had a history of cardiovascular disease compared to participants without a history
No association between high blood pressure and mortality.
29
2
of hypertension (71 versus 58%, chi-squared P ≤ 0.001). Some 62% (n=138) of the participants with a history of hypertension used one or more antihypertensive drugs. Specific medications that were used included (combinations of) β-blockers (n=57, 41%), thiazide diuretics (n=55, 40%), dihydropyridin calcium channel blockers (n=36, 26%), angiotensin converting enzyme inhibitors and angiotensin-1 receptor blockers (n=45, 33%). Of the participants without a history of hypertension, some 20% used one or more of the aforementioned drugs for other diagnosis, as was verified by the general practitioners.
For participants with a history of hypertension, the mean baseline systolic blood pressure was 157.3 mmHg [standard deviation (SD) 18.3] versus 153.7 mmHg (SD 19.1) in those without a history of hypertension (independent t-test, P = 0.03).
In total, 210 participants (36.8 %) had a systolic blood pressure at age 85 of 160 mmHg or higher. The mean diastolic blood pressure at age 85 was 77.0 mmHg (SD 9.9) in participants with a history of hypertension versus 75.8 mmHg (SD 9.2) in those without a history of hypertension (independent t-test, P = 0.01). In total, 48 participants (8.4 %) had a mean diastolic blood pressure above 90 mmHg at age 85.
Table 1 Clinical characteristics at baseline of 571 participants at age 85 years, according to a history of hypertension.
History of Hypertension Present (n=224) Absent (n=347)
Females 160 (71%) 221 (64%)
Low education (%) 151 (68%) 219 (64%)
ADL independency (%) 105 (47%) 154 (45%)
IADL independency (%) 56 (25%) 91 (26%)
Cognitive function
MMSE > 27 points (%) 78 (35%) 124 (36%)
MMSE < 19 points (%) 34 (15%) 58 (17%)
Mean systolic blood pressure (SD) (mmHg) 157.3 (18.3)* 153.7 (19.1) Mean diastolic blood pressure (SD) (mmHg) 77.0 (9.9)* 75.8 (9.2)
History of chronic disease (%) † 131 (59%) 200 (58%)
History of cardiovascular disease (%) ‡ 160 (71%)** 200 (58%) ADL, basic activities of daily livibg; IADL, instrumental activities of daily living; MMSE, Mini -Mental State Examination; SD, standard deviation. * independent t-test P ≤ 0.03, **chi- squared, P ≤ 0.001, † Including diabetes, Parkinson’s disease, chronic obstructive pulmonary disease, arthrosis (including rheumatoid arthritis and polymyalgia rheumatica), and malignancies. ‡ Including cerebrovascular accident, angina pectoris, myocardial infarction, peripheral vascular disease or an electrocardiogram revealing myocardial ischaemia or infarction.
During a median follow-up of 4.2 years, 290 participants died. One hundred and nineteen participants died from cardiovascular causes and 164 from non- cardiovascular causes; causes of death could not be obtained for 7 participants.
Participants with a history of hypertension did not have an increased all-cause mortality risk compared to those without a history of hypertension [adjusted relative risk (RR) 1.19, 95% confidence interval (CI) 0.91-1.55], but they did have a 1.6-fold increased cardiovascular mortality risk (95% CI 1.06-2.40). There was no association between a history of hypertension at age 85 years and non- cardiovascular mortality (Table 2).
Table 2 Mortality risks depending on history of hypertension at age 85 years.
History of hypertension Present (n=224) Absent * (n=347)
All causes († 290) 1.17 (0.90-1.53) 1
Cardiovascular († 119) 1.54 (1.03-2.32) 1
Non-cardiovascular († 164) 0.97 (0.68-1.39) 1
Mortality risks and corresponding 95% confidence intervals were estimated with Cox proportional hazards model adjusted for gender, number of antihypertensive medications and presence of cardiovascular disease. † Observed Number of deaths; * Reference category;
n = number of participants.
Figure 1 presents the cumulative mortality depending on categories of systolic and diastolic blood pressure at baseline. A significantly gradual inverse relation appeared between all-cause mortality and systolic blood pressure. Participants (n=129) with a diastolic blood pressure at baseline below 70 mmHg had a higher all-cause mortality compared to those in the other two categories of diastolic blood pressure.
Table 3 presents the all-cause mortality risks dependent on categories of systolic and diastolic blood pressure at baseline, adjusted for gender, number of antihypertensive medications and presence of cardiovascular disease. Compared to participants with a systolic blood pressure between 140 and 159 mmHg and a diastolic blood pressure between 70 and 89 mmHg (reference group) a 2.3-fold increased mortality risk was found for participants with a blood pressure lower than 140/70 mmHg (95% CI 1.61-3.38).
No association between high blood pressure and mortality.
31
2
Figure 1: Cumulative all cause mortality depending on systolic and diastolic blood pressure at age 85.
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㠀㔀 㠀㘀 㠀㜀 㠀㠀 㠀㤀 㤀 㤀 㤀㈀
䄀最攀 ⠀礀攀愀爀猀 ⤀
Ⰰ Ⰰ㈀
Ⰰ㐀 Ⰰ㘀 Ⰰ㠀
䌀甀洀甀氀愀琀椀瘀攀 洀漀爀琀愀氀椀琀礀
㰀 㐀 洀洀䠀最 ⠀渀㴀 㐀⤀
㸀㴀 㐀 洀洀䠀最 㰀㘀 洀洀䠀最 ⠀渀㴀㈀㔀㜀⤀
㸀㴀 㘀 洀洀䠀最 ⠀渀㴀㈀ ⤀
匀 礀猀 琀漀氀椀挀 䈀 倀
氀漀最 爀愀渀欀 瀀㰀 ⸀
Table 3: Number of participants rates (number of deaths) and relative risks (RR) for all cause mortality dependent on categories of systolic and diastolic blood pressure at baseline.
Systolic BP (mmHg)
Diastolic BP (mmHg) < 140 140 - 159 ≥ 160
< 70
No. participants (no. deaths) 48 (40) 68 (37) 13 (7)
RR (95% CI) 2.33 (1.61-3.38) 1.04 (0.71-1.53) 1.14 (0.52-2.46) 70 – 89
No participants (no. deaths) 56 (31) 180 (93) 158 (58)
RR (95% CI) 1.19 (0.79-1.79) 1* 0.66 (0.47-0.92)
≥ 90
No participants (no. deaths) 0 9 (6) 39 (18)
RR (95% CI) 1.65 (0.72-3.78) 0.82 (0.50-1.36)
BP, blood pressure. Mortality risks and corresponding 95% confidence intervals (CI) were estimated with Cox proportional-hazards model adjusted for gender, number of antihypertensive medications and presence of cardiovascular disease. *, Reference category.
To investigate whether poor general health might be confounding this result an additional adjustment for the presence of chronic diseases, MMSE, ADL and IADL was performed. The increased mortality risk for participants with a blood pressure lower than 140/70 mmHg remained significant (RR 1.51, 95% CI 1.03-2.23). For participants with a systolic blood pressure equal to and higher than 160 mmHg and a diastolic blood pressure between 70 and 89 mmHg, a survival benefit was found compared to the reference group (RR 0.66, CI 0.47-0.92). However, after the additional adjustment for poor general health, this survival benefit disappeared (RR 0.73, 95% CI 0.52-1.02).
The absolute mortality rates dependent on blood pressure at age 85 stratified for the history of hypertension are presented in Table 4. In both strata, all-cause mortality was highest for participants with low blood pressure (systolic blood pressure below 140 mmHg or diastolic blood pressure below 70 mmHg) and most pronounced in participants with a history of hypertension and a low systolic blood pressure. In the group of participants with a systolic blood pressure lower than 140 mmHg, participants with a history of hypertension had a significant higher all-cause mortality rate (29.1 per 100 person years, 95% CI 19.4-38.9) compared to those without a history of hypertension (14.6 per 100 person years, 95% CI 9.9- 19.3).
No association between high blood pressure and mortality.
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Table 4 Absolute mortality rates dependent on blood pressure at baseline stratified for a history of hypertension at age 85 years. Systolic BPHistory of hypertension Diastolic BPHistory of hypertension PresentAbsentPresentAbsent All cause < 14029.1 (19.4-38.9)*14.6 (9.9-19.3)< 70 19.6 (12.1-27.1)17.5 (13.0-21.9) 140-15913.1 (9.2-16.9)12.5 (10.0-15.1)70-8911.7 (9.2-14.3)9.9 (8.0-11.9) ≥ 1608.6 (6.0-11.3)9.2 (6.4-11.9)≥ 90 11.2 (4.9-17.6)12.7 (4.8-20.6) Cardiovascular < 14012.0 (5.7-18.3)6.3 (3.2- 9.4)< 709.8 (4.5-15.1)6.0 (3.4-8.7) 140-1597.1 (4.3-10.0)*3.4 (2.1-4.7)70-895.9 (4.1-7.8) *3.5 (2.4-4.7) ≥ 1604.4 (2.5-6.3)4.1 (2.3-6.0)≥ 904.7 (0.1-8.8)4.2 (0.0-8.4) Non-cardiovascular < 14017.1 (9.6-24.7)*7.9 (4.4-11.4)< 709.8 (4.5-15.1)10.8 (5.5-14.4) 140-1595.6 (3.1-8.2)8.6 (6.5-10.7)*70-895.5 (4.2-7.8)6.1 (4.6-7.6) ≥ 1604.0 (2.2-5.8)5.0 (3.0-7.1)≥ 906.6 (1.7-11.4)8.5 (2.6-14.3) BP blood pressure in mmHg. Data are presented as number of deaths per 100 observed person years at risk and corresponding 95% confidence intervals. * P < 0.05, present versus absent history of hypertension within stratum of blood pressure.
Within the participants with blood pressures lower than 140/70 mmHg at baseline, the amount of cardiovascular disease was not uniformly divided. Of the 48 participants, 16 had a positive history of hypertension. Cardiovascular disease was present in 14 (87.5%) participants with a history of hypertension compared to 18 (56.3%) of the 32 participants without a history of hypertension (chi squared, P = 0.03).
Discussion
The main finding of this prospective population-based study was, that at the age of 85 years and over, high blood pressure was not associated with increased mortality, independently of the history of hypertension. Moreover, subjects with low systolic and diastolic blood pressure had an increased mortality risk.
Except for the lowest range of blood pressures, we did not find a relationship between blood pressure and mortality in participants aged 85 years and over, despite the fact that a history of hypertension remained a risk factor for cardiovascular mortality in this age group. This is different from reports in younger age groups, where those with the highest blood pressure are at the highest mortality risk [1,10-13,22]. The finding that low blood pressure is associated with an increased mortality risk in the oldest old corroborates with earlier results from the Leiden 85-plus Study and other reports [4-6,8,23,24].
The crude results from both cohorts of the Leiden 85-plus Study are similar. Both studies showed a higher mortality for participants in the low blood pressure group. However, in the present study the higher mortality was especially apparent for the participants with a history of hypertension. Secondly, in the present study systolic and diastolic blood pressure were analysed together in blood pressure categories according to international guidelines [21]. This was done because a low diastolic blood pressure in the presence of a high systolic blood pressure might have a different aetiology and thus prognosis, e.g. high atherosclerotic burden, than the same low diastolic blood pressure with a low systolic blood pressure, e.g. heart failure [25].This was confirmed by the finding that a low diastolic blood
No association between high blood pressure and mortality.
35
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pressure is only harmful in the presence of a low systolic blood pressure in the very old.
How can we explain the results? Hypertension is a well-known risk factor for heart failure. Possibly, longstanding hypertension leads to preclinical heart failure that might lower actual blood pressure and therefore could be partly responsible for our finding [26]. Nevertheless, it cannot be excluded that blood pressure- lowering therapy contributed to the inverse relation between low blood pressure and mortality risk.
The strength of the present study is that it seems to reflectthe history of elderly individuals with different levels of blood pressure, given the population-based character, the 87% enrolmentof the 85-year-olds and the small number of individuals who werelost to follow-up. Its weakness is that it relies on a baseline assessmentof blood pressure. Another possible weakness might be the lack of uniformity for a positive history of hypertension. It could be that the general practitioners used variable criteria for a former diagnosis of hypertension.
Moreover, because of the observational natureof the data, we cannot exclude that residual confounding is atplay and therefore we are not able to draw final conclusionson causality.
From the present study, the clear message is that in the oldest old, blood pressure is not a predictor for mortality, again except for those participants with a blood pressure lower than 140/70 mmHg. Our finding supports the general clinical feeling that at old age a blood pressure lower than 140/70 mmHg is relatively rare; in the present cohort only 8.4 % of the participants had blood pressures lower than 140/70 mmHg. This is in sharp contrast to younger age groups where these ranges of blood pressures are considered to be normal. The finding that blood pressures higher than 140/70 mmHg are found not to be associated with mortality risk in the oldest old might have important clinical implications. Moreover, a blood pressure below 140/70 mmHg in the general population of oldest old identifies a new high-risk subgroup. The therapeutic consequences of these findings are unknown and have to be explored in future. The fact that a history of hypertension remains a risk factor for cardiovascular mortality in old age, independent of the current blood pressure, further complicates clinical decision-making.
References
1 Prospectives Studies Collaboration. Age-specific relevance of usual blood pressure to vascular mortality: a meta-analysis of individual data for one million adults in 61 prospective studies. Lancet 2002;360:1903-13
2 Bulpitt CJ, Beckett NS, Cooke J, et al. Results of the pilot study for the hypertension in the very elderly trial. J Hypertens 2003;21:2409-17
3 Gueyffier F, Bulpitt C, Boissel JP, et. al. Antihypertensive drugs in very old people:
a subgroup meta-analysis of randomised controlled trials. Lancet 1999;353:793-6
4 Boshuizen HC, Izaks GJ, Van Buuren S, Ligthart GJ. Blood pressure and mortality in elderly people aged 85 and older. BMJ 1998;316:1780-4
5 Lernfelt B, Svanborg A. Change in blood pressure in the age interval 70-90. Late blood pressure peak related to longer survival. Blood Pressure 2002;11:206-12
6 Heikinheimo RJ, Haavisto MV, Kaarela RH, Kanto AJ, Koivunen MJ, Rajala SA.
Blood pressure in the very old. J Hypertens 1990;8:361-7
7 Glynn RJ, Chae CU, Guralnik JM, Taylor JO, Hennekens CH. Pulse pressure and mortality in old persons. Arch Int Med 2000; 160:2765-72
8 Rajalo S, Haavisto M, Heikinheimo R, Mattila K. Blood pressure and mortality in the very old. Lancet 1983; 322:520-1
9 Vasan RS, Beiser A, Seshadri S, et al. Residual lifetime risk for developing hypertension in middle-aged women and men. The Framingham heart study.
JAMA 2002;287:1003-10
10 Dahlöf B, Lindholm LH, Hansson L, Scherstén B, Ekbom T, Wester P-O. Morbidity and mortality in the swedish trial in old patients with hypertension. Lancet 1991;338:1281-5
No association between high blood pressure and mortality.
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11 SHEP Cooperative Research Group. Prevention of stroke by antihypertensive drug treatment in older persons with isolated systolic hypertension. JAMA 1991;265:3255-64
12 Staessen JA, Fagard R, Thijs L, et al. Randomised double-blind comparison of placebo and active treatment for older patients with isolated systolic hypertension.
Lancet 1997;350:757-64
13 Liu L, Wang JG, Gong L, Liu G, Steassen JA. Comparison of active treatment and placebo in older chinese patients with isolated systolic hypertension. J Hypertens 1998;16:1823-9
14 Hansson L, Lindholm LH, Ekbom T, et al. Randomised trial of old and new antihypertensive drugs in elderly patients: cardiovascular mortality and morbidity the swedish trial in old patients with hypertension-2 study. Lancet 1999;354:1751-6
15 Bootsma-van der Wiel A, van Exel E, de Craen AJ, et al. A high response is not essential to prevent selection bias. Results from the Leiden 85-Plus Study. J Clin Epidemiol 2002;55:1119-25.
16 Exel E, Gussekloo J, Houx P, et al. Atherosclerosis and cognitive impairment are linked in the elderly. The leiden 85-plus Study. Atherosclerosis 2002;165:353-9.
17 WHO, Geneva. International Statistical Classification of Diseases and Related Health Problems 1994.
18 Tombaugh TN, McIntyre NJ. The Mini-Mental State Examination: A comprehensive review. J Am Geriatrics Soc 1992;40:922-35.
19 Kempen GI, Miedema I, Ormel J, Molenaar W. The assessment of disability with the Groningen Activity Restriction Scale. Conceptual framework and psychometric properties. Soc Sci Med 1996;43:1601-10.
20 Macfarlane PW, Latif S. Automated serial electrocardiogram comparison based on the Minnesota code. J Electrocardiol 1996;29 suppl:29-34.
21 Chobanian AV, Bakris GL, Black HR, et al. The seventh report of the joint national committee on prevention detection and treatment of high blood pressure. JAMA 2003; 289:2560-72
22 Staessen JA, Gasowski J, Wang JG, et al. Risks of untreated and treated isolated systolic hypertension in the elderly: meta-analysis of outcome trials. Lancet 2000;355:865-72
23 Askari M, DK Kiely, Lipsitz LA. Is pulse pressure a predictor of cardiovascular complications in a frail elderly nursing home population. Aging Clin Exp Res 2004;16:206-11
24 Glynn RJ, Field TS, Rosner B, Hebert PR, Taylor JO, Hennekens CH. Evidence for a positive linear relation between blood pressure and mortality in elderly people.
Lancet 1995;345:825-9
25 Sutton-Tyrrell K, Alcorn HG, Wolfson Jr SK, Kelsey SF, Kuller LH. Predictors of carotid stenosis in older adults with and without isolated systolic hypertension.
Stroke 1993;24:355-61
26 Himmelmann A. Hypertension: an important precursor of heart failure. Blood pressure 1999;8:253-60
C hapter 3
Prospective study of the effect of blood pressure on renal function in old age;
The Leiden 85-plus Study
Thomas van Bemmel (1), Karen Woittiez (2), Gerard J Blauw (1), Femke van der Sman- de Beer (2), Friedo W. Dekker (2), Rudi G.J. Westendorp (1), Jacobijn Gussekloo (3)
Leiden University Medical Center;
(1) Department of Gerontology and Geriatrics, (2) Department of Clinical Epidemiology,
(3) Department of Public Health and Primary Care.
J Am Soc Nephrol 2006; 17:2561-2566
Abstract
High blood pressure is associated with decline of renal function. Whether this is true for very old people largely is unknown. Therefore, the study assessed the effect of blood pressure on creatinine clearance over time in very old participants.
A total of 550 inhabitants (34% men) of Leiden, The Netherlands, were enrolled in a population-based study at their 85th birthday and followed until death or age 90. Blood pressure was measured twice at baseline and at age 90 years. Creatinine clearance was estimated annually (Cockcroft-Gault formula). The mean creatinine clearance at baseline was 45.4 ml/min (SD 11.5). Systolic blood pressure was not associated with changes in creatinine clearance during follow-up. Those with diastolic blood pressure below 70 mmHg had an accelerated decline of creatinine clearance (1.63 ml/min/year) compared with those with diastolic blood pressures between 70 and 79 mmHg (1.21 ml/min/year; P = 0.01), 80 to 89 mmHg (1.26 ml/min/year; P = 0.03), and higher than 89 mmHg (1.38 ml/min/year; P = 0.32).
Participants with a decline in systolic blood pressure during follow-up had an accelerated decline of creatinine clearance compared with yhose with stable blood pressures (1.54 ml/min/year [SE 0.09] versus 0.98 ml/min/year [SE 0.09]; P <
0.001). Similar results were found for a decline in diastolic blood pressure (1.54 ml/min/year [SE 0.10] versus 1.06 ml/min/year [SE 0.08]; P < 0.001). In the oldest individual, high blood pressure is not associated with renal function. In contrast, low diastolic blood pressure is associated with an accelerated decline of renal function. The clinical implications of these findings have to be studied.
Blood pressure and creatinine clearance at old age.
41
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Introduction
An old age, renal function will be compromised as a result of progressive loss of glomeruli and decline in renal blood flow [1], especially in those with persistent high blood pressure [2]. Because blood pressure increases with age, this implicates a possible double strike for creatinine clearance in the oldest individual [3].
In contrast with younger populations, in the oldest individuals, the association among high blood pressure, mortality and renal function is not straightforward.
The available data suggest that blood pressure lowering above 80 years does not lower overall mortality [4,5]. Data on the effect of blood pressure on morbidity such as renal function are relatively scarce in the oldest individuals [6-8]. One longitudinal report associated blood pressure and renal function in a considerable group of very old Japanese individuals [7]. In that report, high blood pressure was related to an excess decline of serum creatinine. However, an important drawback was the use of serum creatinine for estimation of renal function. In addition, selection bias could have been induced as a result of exclusion of 40% of the participants, who did not attend the reexamination after 3 years.
Although blood pressure lowering in individuals over 80 years might not lower mortality, it is unknown if a high blood pressure might be deleterious for renal function. To investigate whether high blood pressure still is a risk factor for decline in renal function in the oldest individuals, we prospectively studied the effect of blood pressure on changes of creatinine clearance over time in a population-based study of the general population of the oldest individuals.
Materials and Methods
Study population
The Leiden 85-plus Study is a prospective population-based study of all 85-year- old inhabitants of Leiden, The Netherlands. The study design and characteristics of the cohort were described in detail previously [9,10]. In short, between September 1997 and September 1999 all 705 members of the 1912 to 1914-birth cohort in the city of Leiden were asked to participate in the month after their 85th birthday.
There were no selection criteria related to health or demographic characteristics.
Participants were followed until death or the age of 90. At baseline and yearly thereafter, 85-year-old participants were visited at their place of residence. During these visits, participants were weighed, blood pressure was measured, a venous blood sample was drawn, an electrocardiogram was recorded and face-to-face interviews and performance tests were conducted. Information on the medical history was obtained by standardized interviews of the participant’s treating physicians. In addition, information on the use of medication was obtained from the participant’s pharmacist. Participants gave informed consent; for people who were severely cognitively impaired, a guardian gave informed consent. The Medical Ethics Commission of Leiden University approved the study.
Blood pressure
At baseline and at age 90 years, blood pressure was measured twice, with a mean intervening period of 2 weeks. Blood pressure was measured, using a mercury sphygmomanometer, in the seated position after at least 5 min of rest and no vigorous exercise the preceding 30 min. The systolic value was measured at Korotkoff sound 1, and the diastolic value was measured at Korotkoff sound 5.
For the analysis of blood pressure, we used the mean of the measured systolic and diastolic values. For the analysis of pulse pressure, we used the mean systolic minus the mean diastolic blood pressure. Data are presented according to four strata of systolic blood pressure (<140, 140 to149, 150 to 159, and ≥ 160 mmHg), four strata of diastolic blood pressure (<70, 70 to 79, 80 to 89, and ≥ 90 mmHg), and quartiles of pulse pressure. The change of systolic and diastolic blood pressure between ages 85 and 90 was categorized into 3 groups: Declining (≥ 10-mmHg decrease), stable (<10-mmHg increase or <10-mmHg decrease) and increasing (≥
10-mmHg).
Blood pressure and creatinine clearance at old age.
43
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Creatinine clearance
At entry and at yearly intervals thereafter, both the serum creatinine concentration and bodyweight were measured. Creatinine was fully automatically measured according to the Jaffé method (Hitachi 747; Hitachi, Tokyo, Japan). The creatinine clearances were estimated yearly with the Cockcroft-Gault formula as follows [11]:
(140 – Age) x weight (kg) x 1.23
Creatinine clearance = x (0.85 if female)
serum creatinine (μmol/l)
Demographic and clinical characteristics
At baseline, a research nurse collected information concerning the demographic characteristics. The presence of cardiovascular disease was defined as a previous history of cerebrovascular accident, angina pectoris, myocardial infarction, peripheral vascular disease (including a history of arterial grafting, endarterectomy and angioplasty) or an electrocardiogram revealing myocardial ischemia or infarction (Minnesota codes 1-1, 1-2, 1-3, 4-1, 4-2, 4-3, 5-1, 5-2 and 5-3) [12]. The presence of chronic disease was defined as a history of diabetes, Parkinson’s disease, chronic obstructive pulmonary disease, osteoarthritis, or malignancies.
Antihypertensive drugs were classified as usage of angiotensin converting enzyme inhibitor, angiotensin-1 receptor blocker, thiazid diuretic, dihydropyridin calcium channel blocker or β-blocker with the exclusion of Sotacor. We had data on use of anti-hypertensive medication at the ages of 85 and 86.
Statistical analyses
Data were presented as percentages for clinical characteristics and as the mean with standard deviation for continuous variables. The differences in mean creatinine clearances between the categories of blood pressure at baseline were compared with independent t test. The associations over time between creatinine clearance (ml/min) and categories of diastolic and systolic blood pressure were analyzed with a linear mixed model. The creatinine clearance was the dependent factor.
The outcome was the effect on the change in creatinine clearance of the interaction between time and categories of blood pressure. This analysis models the change over time by computing the rate of change for each participant on the basis of all data for that individual adjusted for gender and other possible confounders.
Then the rate of changes for the entire group and the individual deviation from the group rate are computed. This model analyzes the unique effects of individual predictors adjusted for all other fixed and random predictors, accounts for the correlation among repeated measurements on the same participant, and is unaffected by randomly missing data. To investigate the effects of missing data due to mortality, we repeated all analyses with exclusion of participants who died within the first year of follow-up and repeated all analyses with inclusion only of surviving participants who participated up to age 90 years.
An additional analysis was done to examine the effect of a decline in systolic and diastolic blood pressure between ages 85 and 90 on the decline of creatinine clearance in participants who were alive at age 90. The associations between the groups of blood pressure and creatinine clearance were analyzed with a linear mixed model. All analyses were done with software SPSS version 12.0 (SPSS, Inc.
Chicago, IL).
Results
Of the 705 eligible participants, 14 died before they could be enrolled and 92 refused to participate, resulting in a cohort of 599 participants (87 % response). Only one blood pressure measurement was available for 27 participants, serum creatinine at baseline was missing in 11 participants and body weight in 11 participants.
Thus, in these analyses we included 550 participants (Table 1). During follow up, 34 participants declined further participation and 243 participants died (Figure 1). At age 86, 36 participants had started antihypertensive medication and 54 had stopped antihypertensive medication. There were no significant associations between the categories of diastolic and systolic blood pressure and changes of use of antihypertensive medication between ages 85 and 86 years (data not shown).
